This invention relates to generally a vehicular navigation system for providing route guidance according to a set route and, more particularly, to a vehicular navigation system which includes an added function of setting a transit point using an expressway or toll road as a transversal road, so chat a road satisfying a transit point condition can be selected from a plurality of roads to provide guidance to a destination through a transit point set on the road or the selected road.
The navigation system for the vehicle searches for a route from the present position of the vehicle or a designated starting location to the destination based on entry of the location, such as the destination, and provides route guidance based on the route found, thereby providing the driver of the vehicle with information on a route to the destination when the vehicle is traveling on unfamiliar roads. To accomplish this, the vehicular navigation system has a function that enables a route from the present position to the destination be searched for based on entry of the destination, a present position sensing function for sensing the present position and direction of the vehicle, a guidance function for collating the detected present position with a guidance route to provide route guidance along the guidance route, and the like. The guidance function enables the guidance route found by the search processing to be displayed on a map or intersection map, for instance, and the present position and direction of travel of the vehicle to be displayed on the map or intersection map to thereby provide route guidance to the driver. In addition, some navigation systems have a function for providing a driver with information on an intersection at which the vehicle must make a turn, for instance, the remaining distance, its name, and whether turning to the right or left, a function for informing the driver of characteristic features to enable the driver to confirm the guidance route during travel, and a function for providing guidance in the form of not only screen displays but voice or sounds as well.
However, when the route is searched for only using entry of locations, such as the departure location and destination, a route is often found which includes locations the driver does not wish to pass through for reasons such as road conditions and environments or heavy traffic. In this case, processing for calculating another route in lieu of the found route may be envisaged. However, even when this processing is executed, the route found often includes a location the driver does not wish to pass through. Such processing may be performed until a route desired by the driver is found. However, this takes much time to find the desired route, and needs awkward operations because the route to the destination must be calculated a good many times.
Various modification are made to route guidance display screens so that for the confirmation of the present position and direction of travel of the vehicle on the guidance route, the driver can take a quick look at a guidance screen as if the driver were looking at meters. For instance, when the present position and direction of travel of the vehicle are displayed on a map, a guidance route on a map or the like is displayed such that the direction of travel can always turn upward or toward the top of the display. Alternatively, a guidance route on a map display can always be displayed with north at the top of the display, so that an arrow indicating the present position of the vehicle is pointed in the direction of travel. Still alternatively, a mark indicating the present position of the vehicle may blink at a given period so that it can be easily identified (see, for instance, JP-A-58-10708).
In a conventional system where a vehicle's present position mark is blinked, however, it is impossible to reduce an updating time length because the updating of the present position of the vehicle occurs in synchrony with the blinking period. This results in a problem that the distance the present position mark moves across a detailed map each blink is increased, especially when the speed of the vehicle becomes high.
FIGS. 1A-1C illustrates problems associated with the conventional system designed to blink the present position mark of the vehicle. Now consider the case where there are a set of successive intersections with the rearmost one being a guidance intersection at which the vehicle must make a turn, as shown in FIG. 1A. When a distance between adjacent intersections is short, it is impossible for the driver to have a precise indication of the present position of the vehicle in motion, when the present position mark of the vehicle is held, or blinked, off as shown in FIG. 1B. Thus, there is a strong possibility of failing to take notice of the intersection at which the vehicle must make a turn. In other words, it is possible that the driver will make a wrong turn at an intersection situated in front of the rearmost one, as shown in FIG. 1C, or pass straight through the intersection at which the vehicle must make a turn. In this case, the driver will take notice of, with surprise, the fact that the vehicle is off course only after the present position mark is displayed or blinked on. Thus, a grave problem with the present position mark blinking system is that it is difficult to achieve any real-time monitoring of the mark position being displayed.
In a system where a vehicle's present position mark is always displayed, or highlighted without blinking, on the contrary, there is a difficulty in looking at or for characters and marks on a map because they remain hidden by the mark. Moreover, due to no change in the screen being displayed, the user has difficulty noticing the fact that the system (computer) is constantly operating. Especially when the vehicle is at a stop, the screen being displayed is often taken as remaining looked.
Vehicular navigation system having a function for setting a transit point and providing guidance to the destination through the thus set transit point are disclosed in JP-A-2-3899, and JP-A-337216. Conventionally accepted methods for setting the destination include those for providing guidance to the destination via a route found on the basis of the entered destination, for providing guidance to the destination through a first destination via a route found using the destination as a second destination, and for setting a plurality of transit points scheduled to be traversed on a map, so that after the vehicle has passed through a give distance from one scheduled transit point, guidance can be provided to the next scheduled transit point. For instance, JP-A-4-220112 discloses a system for providing guidance to the final guidance point with respect to the set destination.
For destination setting input, one method is known, wherein repeated selection is made from an a list of institutions or facilities, such as, buildings, banks, parks, and playgrounds, to derive a registered destination pre-stored in a storage device to thereby set the registered destination as the destination. In another known method, a map having a center positioned at the location of a registered destination is further scrolled through to set a desired location as the destination.
The object of transit point input is to set a transversal road enabling the user to go to the destination through a selected road, to say nothing of setting the aforesaid transit point as the destination. Currently, it is possible to indiscriminately set the transit point on a drivable road or a nearest drivable road. When the transit point is indiscriminately set on an general road, however, it is impossible to set an expressway or municipal expressway as the transversal road. When a guidance point for the transversal point is indiscriminately set on the nearest general road, however, a problem may arise. For instance, when the transit point is set at a store or other transit point situated alongside an expressway or municipal expressway, route guidance onto the expressway or municipal expressway occurs.
Consider, for example, the case where the user sets the destination without recourse to data on registered locations (location data corresponding to telephone numbers, names of establishments or addresses, which have been stored in a storage device and are selected by the user for setting purposes). For instance, when a cursor is moved from pre-displayed map to set the position of the cursor as the destination, or when the data on registered locations is used to display a map having a center positioned at a location corresponding to the registered location, and a cursor is then moved to set a desired location as the destination, it is required to set a location at which a route search finishes, i.e., a final route guidance location, because the location to be set is often found on a drivable road. In the systems proposed in JP-A-4-220112 and JP-A-6-337216, a point on a road, i.e. one identified in the system, that is nearest to the destination, or transit point, is set as a guidance location, i.e., a final guidance point, or a point scheduled to be traversed, respectively. When the destination, or transit point, is set in this way, it is likely that a point on the road that is nearest to the entered destination, or transit point, is always set as a guidance point by reference to road data. As a result, some difficulty arises, that is, in a congested road area or the like, a guidance point is set on a road that is undesired by the user.